A conventional electrical junction box is generally known as a means for distributing electric power from a shared power source in a vehicle to electronic units, and includes a plurality of bus bars that constitute a distribution circuit and devices such as a switching element integrated into the circuit. Examples of a circuit assembly housed in such an electrical junction box include a circuit assembly disclosed in JP 2005-151617A. This circuit assembly includes a circuit board and a heat dissipation member, which is for dissipating heat from the circuit board, overlaid on the circuit board.
Some elements disposed on a circuit board produce large amounts of heat. It is necessary to intensively dissipate more heat near such electronic components (heat-generating components) that generate large amounts of heat. However, in the conventional circuit assembly disclosed in JP 2005-151617A, a heat dissipation member is overlaid on the entire circuit board and heat overall can be released, but heat cannot be intensively dissipated from a specific portion of the board. Thus, the control apparatus disclosed in JP 2010-180702A is disclosed as being provided with a boss portion that protrudes from a case or a cover to a position near a component, and by applying an insulating heat transfer material to the boss portion, heat from the component can be transferred to the case or the cover. Furthermore, the case or cover of the control apparatus is provided with a protruding surface near a terminal, and by also applying the heat transfer material to the protruding surface, heat can be transferred from the case or the cover via the terminal to a wire harness connected to the terminal.
However, the control apparatus disclosed in JP 2010-180702A (Patent Document 2 listed below) needs to be provided with the protruding boss portion and the protruding surface in order to transfer heat from the component to the case or the cover, which imposes constraints on the design. Additionally, because a heat transfer material such as an adhesive agent needs to be applied to the boss portion and the protruding surface, the number of operation steps increases, and more work is involved because of the need to also increase positioning accuracy in order to reliably abut the boss portion and the protruding surface against each other so as to transfer heat.